Faculdade de Medicina Veterinária e Zootecnia, Universidade de São Paulo, São Paulo, SP, Brazil.
Instituto de Pesquisas Veterinárias Desidério Finamor, Eldorado do Sul, RS, Brazil.
Ticks Tick Borne Dis. 2018 Jul;9(5):1221-1234. doi: 10.1016/j.ttbdis.2018.05.004. Epub 2018 May 4.
Rangelia vitalii is the etiologic agent of canine rangeliosis, a severe piroplasmosis that affects domestic dogs in Brazil, Uruguay and Argentina. While R. vitalii is one of the most pathogenic tick-borne pathogens for dogs in the world, its tick vector has remained unknown. The present study evaluated the vector competence of Rhipicephalus sanguineus sensu lato (both tropical and temperate species), Amblyomma aureolatum, Amblyomma ovale, Amblyomma tigrinum, and Amblyomma sculptum for R. vitalii. These six tick species were selected for the study because they comprise the main tick species infesting dogs within the distribution area of canine rangeliosis in South America. Acquisition feeding of the above six tick species was performed on domestic dogs showing clinical signs of canine rangeliosis, after being experimentally infected through intravenous inoculation or infestation with R. vitalii-infected ticks. Thereafter, engorged ticks were evaluated for transstadial and transovarial passages of R. vitalii through molecular analysis after molting or oviposition and egg hatching. The resultant ticks were evaluated for their competence to transmit R. vitalii to susceptible dogs. Among the six tick species, only A. aureolatum was able to acquire and perpetuate R. vitalii by transstadial and transovarial passages, as demonstrated by >5% infection rates of ticks after hatching or molting. When exposed to transmission feeding, only A. aureolatum ticks were competent to transmit R. vitalii to dogs, which became severely ill, and the results confirmed by molecular methods and blood smear examination to have acquired rangeliosis. Results of the present study, coupled with epidemiological data, indicate that A. aureolatum is a natural vector of R. vitalii. Our results also indicate that R. vitalii is the first Piroplasmorida agent to be transovarially transmitted in Amblyomma ticks.
维氏泰勒虫是犬边虫病的病原体，这种严重的梨形虫病影响巴西、乌拉圭和阿根廷的家犬。虽然维氏泰勒虫是世界上对犬最具致病性的蜱传病原体之一，但它的蜱媒仍然未知。本研究评估了 Rhipicephalus sanguineus sensu lato（热带和温带物种）、南美肩突硬蜱、卵形扇头蜱、小扇头蜱和纹皮扇头蜱对维氏泰勒虫的媒介能力。选择这六种蜱种进行研究，是因为它们构成了在南美洲犬边虫病分布区侵害犬的主要蜱种。在通过静脉接种或感染维氏泰勒虫感染的蜱虫对家犬进行实验感染后，对上述六种蜱种进行了获取性喂养，这些家犬表现出犬边虫病的临床症状。此后，在蜕皮或产卵和卵孵化后，通过分子分析评估吸血后饱血蜱的维氏泰勒虫经胚胎和经卵传递。评估所得的蜱是否有能力将维氏泰勒虫传播给易感犬。在这六种蜱种中，只有 A. aureolatum 能够通过经胚胎和经卵传递来获得和维持维氏泰勒虫，这表现为孵化或蜕皮后蜱的感染率超过 5%。当暴露于传播性喂养时，只有 A. aureolatum 蜱能够将维氏泰勒虫传播给犬，这些犬会患上严重的疾病，并且通过分子方法和血涂片检查确认感染了边虫病。本研究的结果，加上流行病学数据，表明 A. aureolatum 是维氏泰勒虫的天然媒介。我们的结果还表明，维氏泰勒虫是第一个在扇头蜱属蜱中经卵传递的 Piroplasmorida 病原体。
